Ambulatory halo devices are employed in the orthopedic field and are applied to be worn by a patient after surgery or an accident to establish traction on and rigidly immobilize the cervical spine. Such devices generally comprise a supporting vest secured in fixed position on the upper torso of the patient, an adjustable framework mounted on the vest, and a halo member, in the form of an open or closed ring, which is mounted on the framework to reside in a position closely surrounding the skull of the patient. The halo member carries a plurality of adjustable skull pins which are positioned in selected openings around the member and are moved radially inwardly to engage and fix the position of the skull relative to the halo and supporting vest. The support framework attaching the halo member to the vest generally includes adjustable rods which extend upwardly from the vest to the head of the patient and additional adjustment means connecting the rods to the halo member so that the halo member can be variably positioned around the skull above the eyebrow line so that the skull pins engage the skull, fix its position, and establish traction on and immobilize the cervical spine of the patient.
To initially apply an ambulatory halo device to a patient after surgery or accident, the patient wearing the vest of the halo device may be placed in a supine position on a support surface, such as an operating table, with the head maintained in desired position by a medical attendant or a suitable head positioning fixture of the table. Generally, the cervical spine is placed under desired traction by application of an external force to the head through a traction bail, and the halo member positioned at the desired location surrounding the skull of the patient. Skull pins are applied to engage the skull at spaced points therearound and the halo member is then fixed in its position by attachment to the framework of the vest.
After application of the halo device to the patient, the patient is usually x-rayed to determine the precise position of the cervical spine and, if not in the position desired, the halo member is repositioned and fixed in new position by precise adjustment of the supporting framework.
Due to the rigidity and strength required in halo devices to ensure positional fixation of the cervical spine, the halo member and its supporting framework which attach it to the vest generally are formed of high-strength materials, such as stainless steel, aluminum, or the like. Metal ambulatory halo devices, because of their electrical conductance, generally are not compatible with computer-tomography, nuclear magnetic resonance, and x-ray investigation of the body of the patient wearer.
U.S. Pat. No. 4,612,930 discloses a head fixation apparatus including crown and skull pins which serves as a halo device for immobilizing the cervical spine in which the crown, or halo, is perferably formed of a boron fiber or graphite fiber-reinforced plastic to avoid blockage during CT scanning, magnetic resonance imaging, and the like.
U.S. Pat. No. 4,541,421 discloses a halo fixation system which is proported to provide for computer tomography (CT), nuclear magnetic resonance (NMR), and x-ray compatibility of the cervical spine and states that the halo and certain of its supporting assemblies can be made of a composite material, such as an acetyl resin, also known as DELRIN. The patent further states that supporting rods of the assemblies can be carbon graphite rods with a fiberglass internal composition, or other suitable materials. The supporting rods of the halo are attached to the vest and elevation assemblies mounted on the rods support the halo. Free-floating ball and socket assemblies adjacent the ends of the rods permit adjustment in elevational tilt and traction of the skull of the patient.
There is also known in the marketplace an ambulatory halo device which appears to be a modification of the halo fixation system described in U.S. Pat. No. 4,541,421, in which the composite material halo member is adjustably attached through opposed support brackets to four positionally adjustable upstanding support rods of the fixation system. The opposed brackets are located adjacent the sides of the head of the wearer and each is mounted for sliding movement along a horizontal slot of a support arm. Each support arm is connected by ball and socket assemblies to be supported on and interconnect the upper ends of a pair of the four upstanding support rods. The brackets may be moved along the slots to correspondingly move the halo in anterior and posterior directions relative to the head of the patient, and arcuate slots provided in the upstanding brackets permit anterior/posterior tilt adjustment of the halo. Vertical slots in the brackets also permit elevational adjustment of the halo relative to the head of the patient.
Ambulatory halo devices manufactured by AOA All Orthopedic Appliances are also known to comprise a molded plastic vest from which a halo is supported adjacent the patient's head by a rigid metal superstructure including a pair of generally inverted metal U-shaped support members attached by an adjustable cross plate to the anterior and posterior portions of the vest. Mounted on the upper curve portions of the inverted U-shaped members just above the shoulder portions of the vest are a pair of upright turn buckles which supportably engage the lateral sides of the halo to provide for its adjustment.
Certain halo devices are also known to be manufactured by Ace Orthopedic wherein the halo member is supported on upstanding rigid support rods mounted on a vest support and provided with means for adjusting the halo member in several directions, including elevation, anterior/posterior translation, and rotation about a medial axis of the patient.
Although ambulatory halo devices of the prior art permit adjustment of the halo member or ring of the device in multiple directions, it is believed that repositioning movement of the halo in certain directions in such devices results in a temporary loss of support of the position of the halo from the vest along a medial line of the patient's body, resulting in corresponding loss of control of traction on the cervical spine of the patient along the medial axis during these repositioning movements. In other words, if it is desired to adjust the position of the halo member in a certain direction with certain of the prior art devices, the upright supporting rods for the halo member must generally be loosened in or from their supports, either at the vest or at their upper ends, as to allow their axial movement relative to the vest or halo and release the traction applied to the cervical spine along the medial axis of the patient's body during the halo repositioning movement.